sequence

[dolor]

Calculate pi!

No, just kidding. Here's the real one:

Find the nth term of the sequence 1, 2, 4, 7, 11, ...


(if you wanna calculate pi...well, have fun)

[jemidiah]

f(n) = .5n(n-1) + 1

Got it through a quadratic regression, not logic

[Dreamlax]

Slightly off topic, but hasn't one state of America decided that pi should be known as 3 exactly? Probably just a rumour but it wouldn't surprise me.

Tn = n(n - 1)/2 + 1

Same as jemidiah.

[jemidiah]

Actually, that was just a joke that probably got misconstrued somewhere. Some people (ie, me ) memorize Pi to a number of digits (I'm up to 3.14159265358979323642 from memory; every time I see a new one, I tack it on, although that's getting rarer and rarer ).

[Dreamlax]

3.14159 is as far I as ever go. If I need more digits I open Mathematica, or ask someone else who knows .

[DiGiTaIErRoR]

3.1415926535897932384626433832795

[jemidiah]

I've been wrong with the last four digits?!!!!! AHHHHH!!!!!! Oh well

On a seperate note, the Windows XP PowerToy calculator can go up to 512 digits meaning I've got some work to do

[Dreamlax]

Mathematica just gave me 100,000 digits of Pi in less than a second. I love playing around with that program, it seems nothing is too hard for it. I once did Factorial[100000], I left the room and came back and my computer was running low on resources. (I also had 3D Studio MAX idling)

[twanvl]

DiGiTaIErRoR: That's exactly the number of digits the windows caculator gives you
3.1415926535897932384626433832795028841971693993

[sql_lall]

if u just look at the differences in the series, you get 1, 2, 3, 4...
look familiar? Hence the triangular numbers, +1

[dolor]

you know what's crazy...those people that memorize pi to like past 100 digits... ugh

no offense to anyone out there, i just think it's crazy

[DiGiTaIErRoR]

Originally posted by twanvl
DiGiTaIErRoR: That's exactly the number of digits the windows caculator gives you
3.1415926535897932384626433832795028841971693993

Coincidence? I think not!

[Spajeoly]

Well, not like it's really ever needed, but if you want to take it farther you could let this page run for a while.

[Acidic]

Well, using the prgram I made on my TI83 last summer I get:
Un = .5n^2 -.5N+1
Which i suppose is the same as:
Un = .5n(n-1)+4

Oh, god I just realised this thread is slightly out of date, oh well.

[Spajeoly]

You and me both, pal.

Look at the date on my last post here.

But it aint that out of date, only a few days really. I was just all happy to have something to post about in the math forums, I am more then out of my element here.